In some cases, it may be useful to wait to gather some data before making a prediction. A post with very few comments after a few hours is unlikely to receive many more. Conversely, a post that garnered lots of immediate attention and has a large comment thread is likely to receive more comments and further attention [1]}, [2]}. Fig. REF  illustrates this dynamic for comment threads in the /r/worldnews/ subreddit. We observe that initial comment velocity is highly predictive of the final comment thread size. For example, if a post in the /r/worldnews/ subreddit receives 5 or more comments in the first half-hour, the final cascade will, on average, consist of 90.53 comments; if the post has fewer than 5 comments in the same period, the final cascade will, on average, only contain 5.07 comments.
